On 10/28/22 02:23, John Garry wrote: > On 27/10/2022 14:02, Hannes Reinecke wrote: >>>>> /** >>>>> * ata_scsi_slave_config - Set SCSI device attributes >>>>> * @sdev: SCSI device to examine >>>>> diff --git a/include/linux/libata.h b/include/linux/libata.h >>>>> index 8938b584520f..f09c5dca16ce 100644 >>>>> --- a/include/linux/libata.h >>>>> +++ b/include/linux/libata.h >>>>> @@ -1141,6 +1141,8 @@ extern int ata_std_bios_param(struct >>>>> scsi_device *sdev, >>>>> sector_t capacity, int geom[]); >>>>> extern void ata_scsi_unlock_native_capacity(struct scsi_device >>>>> *sdev); >>>>> extern int ata_scsi_slave_config(struct scsi_device *sdev); >>>>> +extern int ata_internal_queuecommand(struct Scsi_Host *shost, >>>>> + struct scsi_cmnd *scmd); >>>>> extern void ata_scsi_slave_destroy(struct scsi_device *sdev); >>>>> extern int ata_scsi_change_queue_depth(struct scsi_device *sdev, >>>>> int queue_depth); >>>>> @@ -1391,7 +1393,8 @@ extern const struct attribute_group >>>>> *ata_common_sdev_groups[]; >>>>> .slave_destroy = ata_scsi_slave_destroy, \ >>>>> .bios_param = ata_std_bios_param, \ >>>>> .unlock_native_capacity = ata_scsi_unlock_native_capacity,\ >>>>> - .max_sectors = ATA_MAX_SECTORS_LBA48 >>>>> + .max_sectors = ATA_MAX_SECTORS_LBA48,\ >>>>> + .reserved_queuecommand = ata_internal_queuecommand >>>>> #define ATA_SUBBASE_SHT(drv_name) \ >>>>> __ATA_BASE_SHT(drv_name), \ >>>> >>> >> >> But that means we can't use it before the SCSI host is initialized; some >> HBAs require to send commands before the host can be initialized properly. > > At what stage do you want to send these commands? The tags for the shost > are not setup until scsi_add_host() -> scsi_mq_setup_tags() is called, > so can't expect blk-mq to manage reserved tags before then. > > If you are required to send commands prior to scsi_add_host(), then I > suppose the low-level driver still needs to manage tags until the shost > is ready. I guess that some very simple scheme can be used, like always > use tag 0, since most probe is done serially per-host. But that's not a > case which I have had to deal with yet. In libata case, ata_dev_configure() will cause a lot of ata_exec_internal_sg() calls for IDENTIFY and various READ LOG commands. That is all done with non-ncq commands, which means that we do not require a hw tag. But given that you are changing ata_exec_internal_sg() to call alloc_request + blk_execute_rq_nowait(), how would these work without a tag, at least a soft one ? Or we would need to keep the current code to use ata_qc_issue() directly for probe time ? That will look very ugly... > > Thanks, > John -- Damien Le Moal Western Digital Research
